FIG. 1 illustrates one common internal structure of magnetic transducer 20 (also called a head) which can be used in a magnetic disk drive. The features are not drawn to scale, since the wide range of thicknesses would make the smaller features indistinct. Except as noted below all of the features discussed herein are sized according to the prior art. The thin film protective layer 45 and the adhesion layer 43 protect the vulnerable elements such as the magnetoresistive sensor 35, shields S1 and S2, and pole pieces P1, P2 and P3 which are commonly made of NiFe. The surface of the protective layer 45 is at the air-bearing surface (ABS) for the transducer which confronts the surface of the rotating disk (not shown). The combined thickness of the adhesion and protective layers limits how close the magnetoresistive sensor 35 and other elements of the transducer are to the magnetic media of the disk and, therefore, limits the areal density of information that can be written on and read from the disk.
In U.S. Pat. No. 6,503,406 to Hsiao, et al. the use of a silicon adhesion layer with a carbon protective layer for a magnetic transducer is described. Grill, et al., in U.S. Pat. No. 5,159,508 disclose a dry process for forming a protective coating over the slider prior to the lithographic process. The protective coating comprises two layers, the first layer an adhesion layer, e.g. silicon, and a second layer of amorphous carbon. The ABS is then formed on the slider covered with the protective coating.
U.S. Pat. No. 6,086,730 to Liu, et al., describes a method for sputtering a carbon protective layer with a high sp3 bond content which involves applying relatively high voltage pulses to the carbon target. Liu ′730 asserts that the resulting carbon overcoat has good durability and corrosion resistance down to low thicknesses. In addition to the pulsed DC sputtering with above mentioned characteristics, Liu also notes that the substrate can have a negative voltage bias in order to enhance the ta-C:H characteristics of the carbon film. Nominally the substrate is biased negative to the ground, so that there is potential of additional bombardment of the substrate by the argon ion used to sputter the target or to accelerate the carbon ions that may have formed during sputtering at high target bias potential. When substrate bias is applied, the positive ions of carbon and argon will be accelerated toward the substrate during deposition. Liu does not note, however, that argon atoms can be incorporated in the carbon film with undesirable results.
In the typical sputtering process, the atmosphere of the reaction chamber contains a noble gas which is most commonly argon, but helium, neon, krypton, and xenon are commonly mentioned as alternatives. (See for example, U.S. Pat. No. 6,569,293 to Makowiecki, et al.)
In U.S. published application No. 20030113588, Jun. 19, 2003, Uwazumi, Hiroyuki, et al. indicate that the concentration of the atoms of one of the inert gases remaining in the underlayer on a magnetic thin film disk is reduced by mixing the one inert gas with a different inert gas having larger atomic weight and radius. The magnetic layer is laminated onto the underlayer. The underlayer is deposited in a gas atmosphere containing argon and at least one of krypton and xenon in an amount sufficient to reduce the argon remaining in the underlayer to less than 1,000 ppm. Such a gas atmosphere contains at least 10% of krypton or xenon, and pressurized to a range of 30-70 mTorr. The underlayer is formed with a film structure composed of fine grains, which are suitable for epitaxial growth of the magnetic layer.
In U.S. Pat. No. 6,236,543 Han, et al., describe the use filtered cathodic arc (FCA) deposition to form landing pads for a slider air-bearing surface (ABS) of tetrahedral amorphous carbon (t-aC). The t-aC is extremely hard and highly stressed. The pads are fabricated after the slider has been coated with an adhesion layer such as Si, SiC, SiO2 or Si3N4, and a carbon overcoat of diamond-like-carbon (DLC) or t-aC has been formed. The pads are formed by filtered cathodic arc deposition, which uses carbon ions from a graphite cathode and a filter that removes macroparticles. The resulting t-aC material is said to have properties virtually equal to those of diamond, including high stress and hardness associated with nearly ubiquitous sp3 bonds. Other benefits of t-aC are a reduction in surface energy and wettability.
In order to improve the performance of magnetic thin film transducers the protective overcoat 45 and the adhesion layer 43 must be made as thin as possible to reduce the separation from the magnetic media and still maintain the protective function.